PayPal's protection is kinda iffy. If you read the fine print you'll see that even if they find in your favor they can only refund the money if the person you sent money to still has money in his PayPal account. If he's the type of person that withdraws his PayPal money as soon as he gets it then you're out of luck. I know this because I've attempted to get my money back on a PayPal transaction before.
Kinda. But that only works the once. If you're a seller of a single item, you might get away with it; if you're like me and sell over a thousand transactions every month, it won't work.
Basically, if you want any kind of regular or repeat business using PayPal, as a seller you can't do that.
If the seller's funding source fails when PayPal attempts to refund the customer, that funding source is cut off by PayPal. Without that funding source, the seller's PayPal account ceases to be functional for most transactions.
So, say I had 1000 subscribers. I could choose to screw one guy over for $3. But to do that, I'd have to invalidate my funding source (bank account) so that he couldn't get a refund, at which point it would be cut off by PayPal. I'd immediately be unable to receive my $3 from the other 999 subscribers. For the sake of $3 I'd lose nearly $3000 - that month; rinse and repeat. Not to mention the PITA factor of emptying my bank account and moving my wordly wealth to another account.
So it's highly in my interests to ensure that in such situations, the customer gets his refund.
Now, of course that's open to abuse - the customer can do that whenever he likes, and PayPal puts the onus on me - the seller - the prove that I supplied the product or service (which is very difficult for me to do). PayPal has a procedure in place for people who do that a lot. As do I.
As with all transactions, you need to look at who you're doing business with. Is this person in a position to cash and burn? Or does this person need to maintain the PayPal cash flow? If the former - be cautious. If the latter - you're safe, unless the seller's insane.